I couldn't finish 'em. Looks like this's gonna get complicated.
The Left Arm is an enemy in Final Fantasy IV: The After Years. It is fought in the bottommost levels of the Depths, alongside the Right Arm. It will either attack with a weak physical attack, or use Stone Touch to inflict Gradual Petrify to one party member, Slap to inflict various statuses to one party member, or attempt to inflict Instant Death with Crush. Otherwise, it is not a difficult enemy to defeat despite its high HP.